This invention relates to sealing devices, and more particularly to a seal assembly for effecting a fluid-tight seal between adjacent surfaces of wellhead components such as between a tubing hanger and a tubing head.
With high pressure wellheads where fluid pressures in the order of 20,000 p.s.i. and higher are encountered, conventional sealing devices for preventing well fluids from blowing or leaking at the surface are oftentimes inadequate to the task. At very high pressures, it has been necessary to resort to non-extrudible metal seals which provide for metal-to-metal sealing surfaces. Such sealing devices have been used to seal around pipe hangers in a wellhead and typically utilize the weight of the tubing or casing string and the fluid pressure for compressing the sealing device to effect a seal. While such high pressure metallic seals are well known, as shown in U.S. Pat. Nos. 3,104,121 and 3,166,345, these have only met with limited success. The axial elongation effected by compression of these seals inhibit their sealing effectiveness by reducing the radial forces exerted by these seals with the surfaces with which they must coact.